This invention relates to reflection-type projection screens. More particularly, the invention relates to reflection-type projection screens having excellent reflection directivity in the horizontal and vertical directions yet which produce a reflected image having superior gain and contrast.
The desirability of producing reflection-type projection screens having a wide angle of reflectivity with suitable contrast is well known. In settings such as movie theaters and home viewing areas, the viewer is often times positioned at a significant angle with respect to the direction of the projected image from the projector, i.e. the direction of incident projected light. Therefore, the screen must have an effective viewing angle greater than would be producible if a highly reflective medium were used alone.
Numerous attempts have been made to remedy this problem. U.S. Pat. No. 3,653,740 to Ogura (“'740 Patent”) discloses a projection screen having a double rolled aluminum foil sheet attached to a support member, and a brushed resin film covering the foil as a protective coating against scratching, fingerprints, etc. No mention is made of the brushing techniques used or of the resulting surface characteristic of the resin film after it is brushed.
U.S. Pat. No. 6,144,491 to Orikasa (“'491 Patent”) discloses a reflection-type projection screen having a substrate, a light reflecting layer made from a transparent resin in which flakes of a light-reflective material are dispersed, and a transparent light-diffusing layer made from a transparent resin in which fine crystalline particles of calcite and a pigment are dispersed. The films of '491 Patent are complicated, expensive and particularly difficult to achieve.
U.S. Pat. No. 6,040,941 to Miwa (“'941 Patent”) discloses a reflection-type projection screen having a light-reflecting substrate laminated to a light-transmitting polymer layer having light absorptive slits or “crazes” of regular directionality disposed therein. The slits are filled with a light-absorbing substance such as a black pigment or dye.
U.S. Pat. No. 6,233,095 BI to Niwa (“'095 Patent”) discloses a reflex-type screen comprised of a first layer formed integrally with an inner reflex layer on a surface of a substrate, and a second layer formed of a deflection film bonded to a surface of the first layer. The screen of the '095 Patent was developed to facilitate the use of screens which can be deflected, e.g. rolled up when not in use. Beads such as acrylic or silicon beads are applied to the substrate surface prior to deposition of a metal reflective layer, rendering the process of attaching the metal reflective layer all the more complicated.
U.S. Pat. No. 5,456,967 to Nezu (“'967 Patent”) discloses a reflection-type screen of the type that can be wound up in a roll form and unwound as needed and comprises a substrate sheet to which is laminated a high-density light diffusion-reflection layer and a translucent light diffusion layer including a soft vinyl chloride sheet, the translucent light diffusion layer having a surface provided with a light-diffusing fine uneven pattern.
U.S. Pat. No. 5,361,163 to Matsuda (“'163 Patent”) discloses a reflection-type projection screen comprising a dark plastic substrate, a fibrous sheet of glass fibers, a white, opaque base material sheet and a light diffusing layer of a translucent plastic onto which a lustrous pigment or calcite powder is incorporated. An emboss is formed on the outer surface of the light diffusion layer. Light absorbing strips are provided each at a position corresponding to a concave portion of the emboss on the surface of the base material sheet adjoining the light diffusing layer.
U.S. Pat. No. 5,148,309 to Yamada (“'309 Patent”) discloses a reflective type screen comprising a reflective surface layer, a polarizing plate layer in position in front of the reflective surface layer, and a diffusion layer located in front of the polarized plate layer, wherein the reflective surface layer, the polarizing plate layer and the diffusion layer are laminated together using an adhesive to form an integral structure. Additional embodiments are disclosed in the '309 Patent, all of which require a polarizing layer, perhaps to accommodate exotic applications of projection images onto a screen.
U.S. Pat. No. 4,232,939 to Kikuchi (“'939 Patent”) discloses a transparent base plate to which is attached on one side an aluminum mirror surface and on the other side a diffusing specular layer of low diffusing performance. The diffusing performance of the diffusing specular layer can be adjusted as desired while the reflection performance of the mirror surface is constant. The diffusing specular layer is formed with a plurality of elongated columnar lenticles having convex surfaces facing the viewer. The curvature of the lenticles is determined by the distance between the screen and the viewers. The outer convex surface of the lenticles is treated by sandblasting. The lenticles are arranged in a vertically elongated pattern, which sacrifices vertical directivity.
U.S. Pat. No. 4,201,449 to Campion (“'449 Patent”) teaches a front projection screen having a substrate, a reflective aluminum ink coating applied to a surface of a substrate, and a protective coating, preferably of a clear acrylic having a gloss finish for the purpose of protecting the reflective film. The disclosure specifies that the coating reduces somewhat the reflective efficiency of the screen. Therefore, the directionality of such a screen is likely to be extremely narrow.
U.S. Pat. No. 4,190,320 to Ferro (“'320 Patent”) teaches a front projection screen having two reflecting layers separated by a light transmissive layer, and a light-diffusing surface coating provided on the frontmost reflecting layer. The screen forms an embossed pattern across its front surface.
U.S. Pat. No. 4,089,587 to Schudel (“'587 Patent”) discloses a projection screen having a film which is constructed of a partially deformable, resilient material. One surface of the film has in combination a random matte texture and a substantially unidirectional striated, i.e. grooved, texture. A layer of reflective material is deposited on the above-mentioned surface of the film to provide a high gain, damage resistant reflective surface. The screen of the '587 Patent is intended to be of the double-coverture type, i.e. curved about at least two axes so as to focus the reflected image in a confined area. Another embodiment of the '587 Patent discloses a flat screen. Striations are provided, usually vertically aligned to disburse the light reflected off of the reflective film. The arrangement of the striations or lenticles as vertical grooves limits the directionality to nearly a side-by-side viewing field and not top to bottom or diagonal.